CN113748596A

CN113748596A - Motor control device

Info

Publication number: CN113748596A
Application number: CN202080032244.1A
Authority: CN
Inventors: 山田纯; 中山诚二; 坂口浩二; 宫野遥
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2019-05-08
Filing date: 2020-05-07
Publication date: 2021-12-03
Anticipated expiration: 2040-05-07
Also published as: US11996794B2; JP2020184840A; WO2020226156A1; CN113748596B; DE112020002260T5; JP7230674B2; US20220060138A1

Abstract

The present invention relates to a motor control device. A motor control device (40) controls driving of a motor (10) having a coil (11), and is provided with a drive circuit (41) and a control unit (50). The drive circuit (41) has a plurality of switching elements (411-416) and switches the energization of the counter coil (11). The control unit (50) has an energization control unit (65) and a current limiting unit (62). An energization control unit (65) controls energization to the coil (11) so that the motor (10) is accelerated and then decelerated to stop the rotational position of the motor (10) at a target rotational position. A current limiting unit (62) limits the current during deceleration control.

Description

Motor control device

Cross reference to related applications: the present application is based on japanese patent application No. 2019-088390, filed 5, 8, 2019, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates to a motor control device.

Background

Conventionally, in a shift range control device, driving of a motor is controlled so that the motor stops at a target position. For example, in patent document 1, the driving of the motor is controlled by switching the control to acceleration control, stabilization control, deceleration control, sudden braking control, and stationary phase energization control.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-135919

Disclosure of Invention

In patent document 1, the duty ratio when positive torque is output is defined as positive, the duty ratio when negative torque is output is defined as negative, and the duty ratio at the start of deceleration control is set to-100 [% ]. When the control is performed in this manner, an induced electromotive force may cause an overcurrent. The invention aims to provide a motor control device capable of restraining overcurrent.

The motor control device of the present invention controls driving of a motor having a coil, and includes a drive circuit and a control unit. The drive circuit has a plurality of switching elements and switches energization to the coil. The control unit has an energization control unit and a current limiting unit.

In claim 1, the energization control unit controls energization of the coil so that the motor is accelerated and then decelerated to stop the rotational position of the motor at the target rotational position. The current limiting unit limits a current during deceleration control. In claim 2, the energization control unit controls energization of the coil by changing the duty ratio so that the motor is accelerated and then decelerated to stop the rotational position of the motor at the target rotational position. The current limiting unit calculates a duty limit value that limits a duty. The duty limit value is corrected based on the current when the current is supplied at a constant duty before the deceleration control is started. This can suppress overcurrent.

Drawings

The above objects, and other objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. The attached drawings are that,

fig. 1 is a perspective view showing a shift-by-wire system according to embodiment 1;

fig. 2 is a schematic configuration diagram showing a shift-by-wire system according to embodiment 1;

fig. 3 is a circuit diagram showing a motor and a drive circuit according to embodiment 1;

fig. 4 is a block diagram showing a shift range control device of embodiment 1;

fig. 5 is an explanatory diagram for explaining the induced electromotive force with the positive duty ratio according to embodiment 1;

fig. 6 is an explanatory diagram for explaining the induced electromotive force when the duty ratio of embodiment 1 is negative;

fig. 7 is an explanatory diagram for explaining the relationship among the motor rotation speed, the coil current, and the duty ratio at the time of deceleration control according to embodiment 1;

fig. 8 is a map showing a lower duty ratio limiting unit and an upper duty ratio limiting value in the reference voltage according to embodiment 1;

fig. 9 is a map of the correction coefficients of embodiment 1;

fig. 10 is a timing chart illustrating the motor drive control according to embodiment 1;

fig. 11 is a flowchart for explaining the limited duty ratio calculation processing according to embodiment 2;

fig. 12 is a timing chart for explaining the motor drive control of embodiment 2;

fig. 13 is a flowchart for explaining the limited duty ratio operation processing according to embodiment 3;

fig. 14 is a map showing a reference current according to the motor rotation speed according to embodiment 3;

fig. 15 is a timing chart for explaining the motor drive control of embodiment 3;

fig. 16 is a timing chart for explaining the motor drive control of the reference example.

Detailed Description

Hereinafter, a motor control device according to the present invention will be described with reference to the drawings. In the following, in the embodiments, substantially the same components are denoted by the same reference numerals, and description thereof is omitted.

(embodiment 1)

Fig. 1 to 10 show embodiment 1. As shown in fig. 1 and 2, the shift-by-wire system 1 includes a motor 10, a shift range switching mechanism 20, a parking lock mechanism 30, a shift range control device 40, and the like. The motor 10 is rotated by electric power supplied from a battery, not shown, mounted on a vehicle, not shown, and functions as a drive source of the shift range switching mechanism 20. The motor 10 of the present embodiment is a permanent magnet DC brushless motor. As shown in fig. 3, the motor 10 has a coil 11. Coil 11 is formed of U-phase coil 111, V-phase coil 112, and W-phase coil 113, and wound around a stator, not shown.

As shown in fig. 2, the encoder 13 detects a rotational position of a rotor, not shown, of the motor 10. The encoder 13 is, for example, a magnetic rotary encoder, and is configured by a magnet that rotates integrally with the rotor, a hall IC for magnetic detection, and the like. The encoder 13 outputs encoder signals, which are pulse signals of a phase and B phase, at predetermined angular intervals in synchronization with the rotation of the rotor.

The speed reducer 14 is provided between a motor shaft of the motor 10 and the output shaft 15, and reduces the rotation of the motor 10 to output the reduced rotation to the output shaft 15. Thereby, the rotation of the motor 10 is transmitted to the shift range switching mechanism 20. An output shaft sensor 16 that detects the angle of the output shaft 15 is provided for the output shaft 15. The output shaft sensor 16 is, for example, a potentiometer.

As shown in fig. 1, the shift range switching mechanism 20 includes a detent plate 21, a detent spring 25, and the like, and transmits the rotational driving force output from the reduction gear 14 to the manual valve 28 and the parking lock mechanism 30.

The stopper plate 21 is fixed to the output shaft 15 and driven by the motor 10. A pin 24 protruding parallel to the output shaft 15 is provided on the stopper plate 21. The pin 24 is connected to a manual valve 28. The stopper plate 21 is driven by the motor 10, whereby the manual valve 28 reciprocates in the axial direction. That is, the shift range switching mechanism 20 converts the rotational motion of the motor 10 into a linear motion and transmits the linear motion to the manual valve 28. The manual valve 28 is provided to the valve body 29. By the manual valve 28 moving back and forth in the axial direction, the hydraulic pressure supply path to the hydraulic clutch, not shown, is switched, and the engagement state of the hydraulic clutch is switched, whereby the shift range is changed.

On the stopper plate 21, 4 recesses 22 for holding the manual valve 28 at positions corresponding to the respective ranges are provided on the stopper spring 25 side. The concave portion 22 corresponds to each range of D (drive), N (neutral), R (reverse), and P (parking) from the base side of the detent spring 25.

The stopper spring 25 is an elastically deformable plate-like member, and a stopper roller 26 is provided at the tip end thereof. The stopper roller 26 is fitted into any one of the recesses 22. The stopper spring 25 biases the stopper roller 26 toward the rotation center side of the stopper plate 21. When a rotational force of a predetermined value or more is applied to the stopper plate 21, the stopper spring 25 is elastically deformed, and the stopper roller 26 moves in the recess 22. By fitting the detent roller 26 into any one of the recesses 22, whereby the swing of the detent plate 21 is restricted, the axial position of the manual valve 28 and the state of the parking lock mechanism 30 are determined, and the shift range of the automatic transmission 5 is fixed.

The parking lock mechanism 30 has a parking lever 31, a cone 32, a parking lock cylinder 33, a shaft portion 34, and a parking gear 35. The parking lever 31 is formed in a substantially L-shape, and one end 311 side is fixed to the stopper plate 21. A cone 32 is provided on the other end 312 side of the parking lever 31. The cone 32 is formed so as to be reduced in diameter toward the other end 312 side. When the stopper plate 21 is rotated in a direction in which the stopper roller 26 is fitted into the recess corresponding to the P range, the cone 32 moves in the direction of the arrow P.

The parking lock cylinder 33 abuts against the conical surface of the cone 32 and is provided swingably about the shaft 34. A convex portion 331 capable of meshing with the parking gear 35 is provided on the parking gear 35 side of the parking lock column 33. When the cone 32 is moved in the arrow P direction by the rotation of the detent plate 21, the parking lock cylinder 33 is pushed up, and the projection 331 engages with the parking gear 35. On the other hand, when the cone 32 moves in the arrow NotP direction, the engagement of the convex portion 331 and the parking gear 35 is released.

The parking gear 35 is provided on an axle, not shown, and is provided so as to be capable of meshing with the convex portion 331 of the parking lock column 33. When the parking gear 35 engages with the projection 331, the rotation of the axle is restricted. When the shift range is the NotP range, which is a range other than P, the parking gear 35 is not locked by the parking lock column 33, and the parking lock mechanism 30 does not interfere with the rotation of the axle. When the shift range is the P range, the parking gear 35 is locked by the parking lock column 33, and the rotation of the axle is restricted.

As shown in fig. 2 and 3, the shift range control device 40 includes a drive circuit 41, an ECU50, and the like. The drive circuit 41 is a three-phase inverter that switches the energization of the coil 11, and the switching elements 411 to 416 are bridged. One end of the U-phase coil 111 is connected to a connection point of the switching

elements

411 and 414 which form the U-phase of the pair. One end of the V-phase coil 112 is connected to a connection point of the pair of V-

phase switching elements

412 and 415. One end of the W-phase coil 113 is connected to a connection point of the W-

phase switching elements

413 and 416 forming the pair. The other ends of the coils 111-113 are connected by a wire connection part 115.

A current sensor 42 for detecting the current of the coils 111-113 is provided between the drive circuit 41 and the ground. The current sensor 42 includes a U-phase current sensor 421 that detects the current of the U-phase coil 111, a V-phase current sensor 422 that detects the current of the V-phase coil 112, and a W-phase current sensor 423 that detects the current of the W-phase coil 113. Hereinafter, the respective phase currents detected by the current sensors 421 to 423 are collectively referred to as a coil current Ic.

The ECU50 is mainly composed of a microcomputer or the like, and includes therein a CPU, a ROM, a RAM, an I/O, a bus connecting these components, and the like, all of which are not shown. Each process in the ECU50 may be a software process performed by the CPU executing a program stored in advance in an actual storage device (i.e., a readable and non-transitory tangible storage medium) such as a ROM, or may be a hardware process performed by a dedicated electronic circuit.

As shown in fig. 2, the ECU50 controls the driving of the motor 10 based on a shift signal corresponding to a driver's request for a shift range, a signal from a brake switch, a vehicle speed, and the like, thereby controlling the switching of the shift range. The ECU50 controls the drive of the transmission hydraulic pressure control solenoid 6 based on the vehicle speed, the accelerator opening, the driver's requested shift range, and the like. The gear shift stage is controlled by controlling the hydraulic control solenoid 6 for gear shift. The hydraulic control solenoids 6 for gear shift are provided in the number corresponding to the number of gear shift stages and the like. In the present embodiment, one ECU50 controls the driving of the motor 10 and the solenoid 6, but may be divided into a motor ECU for controlling the motor 10 and an AT-ECU for controlling the solenoid. Hereinafter, the drive control of the motor 10 will be mainly described.

As shown in fig. 4, the ECU50 includes, as functional blocks, an encoder count calculation unit 51, a rotational speed calculation unit 52, a target count setting unit 55, a count difference calculation unit 56, a target speed setting unit 57, a requested torque calculation unit 61, a duty limit value calculation unit 62, an output duty calculation unit 63, an energization control unit 65, and the like. The ECU50 controls the driving of the motor 10 so that the encoder count value Cen stops at a target count value Cen set in accordance with the requested range. Specifically, when the range switching is requested, the motor 10 is subjected to acceleration control, and when the motor rotation speed SP reaches a predetermined speed, after stable control is performed to maintain the rotation of the motor 10 at that speed, deceleration control is performed, and the motor 10 is stopped so that the encoder count value Cen falls within a predetermined control range including the target count value Cen. In the present embodiment, the driving of the motor 10 is controlled by PWM control. Hereinafter, the duty ratio in the PWM control is appropriately simply referred to as "duty ratio".

The encoder count calculation unit 51 calculates an encoder count value Cen, which is a count value of the encoder 13, based on the a-phase and B-phase pulses output from the encoder 13, the encoder count value Cen being a value corresponding to the actual mechanical angle and electrical angle of the motor 10. The rotational speed calculation unit 52 calculates the rotational speed of the motor 10, i.e., the motor rotational speed SP, based on the a-phase and B-phase pulses output from the encoder 13. In the present embodiment, the motor rotation speed SP is a so-called rotation speed expressed by a unit rpm or the like, but an angular speed or the like may be used.

The target count setting unit 55 sets a target count value Cen corresponding to a shift range requested by the driver input by an operation of a shift lever or the like, not shown. The count difference calculation unit 56 calculates a count deviation Δ Cen, which is the difference between the target count value Cen and the encoder count value Cen. The count deviation Δ Cen may be a remaining count until the target count. The target speed setting unit 57 calculates the target motor rotation speed SP based on the count deviation Δ Cen and the battery voltage VB.

The requested torque calculation unit 61 calculates the requested torque Trq based on the speed deviation Δ SP that is the difference between the target motor rotation speed SP and the motor rotation speed SP. Duty limit value calculation unit 62 calculates lower duty limit value Dlim _ l and upper duty limit value Dlim _ h based on motor rotation speed SP.

The output duty ratio calculation unit 63 calculates the output duty ratio D based on the requested torque Trq, the coil current Ic, and the duty ratio limit values Dlim _ l and Dlim _ h. The energization control unit 65 performs PWM processing based on the output duty D to generate a control signal for controlling the on/off operation of the switching elements 411 to 416. The generated control signal is output to the drive circuit 41. In fig. 4, the driving circuit is described as "MD".

Here, the positive and negative of the coil current Ic and the duty ratio will be described. In this specification, the coil current Ic and the duty ratio when the motor 10 outputs positive torque are defined as positive values, and the coil current Ic and the duty ratio when the motor 10 outputs negative torque are defined as negative values. Specifically, the coil current Ic and the duty ratio are positive when the torque in the direction to rotate the motor 10 in the range switching direction is output, and the coil current Ic and the duty ratio are negative when the torque in the direction to stop the motor 10 is output.

The induced electromotive force of the motor 10 will be described with reference to fig. 5 and 6. Fig. 5 shows a case where the coil current Ic and the duty ratio are positive, and fig. 6 shows a case where the coil current Ic and the duty ratio are negative. In fig. 5 and 6, a voltage Vi generated by induced electromotive force is indicated by a battery symbol surrounded by a double-dashed line circle, an induced current Ii which is a current generated by induced electromotive force is indicated by a double-dashed line arrow, and a coil current Ic is indicated by a broken line arrow. In order to avoid complication, some symbols are omitted.

As shown in fig. 5, when the coil current Ic and the duty ratio are positive and the acceleration torque is generated, the direction in which the power supply voltage is applied and the direction in which the induced electromotive force is applied are opposite, and thus the overcurrent due to the induced electromotive force is not generated.

On the other hand, as shown in fig. 6, when the coil current Ic and the duty ratio are negative and the braking torque is generated, the direction in which the power supply voltage is applied and the direction in which the electromotive force is induced are the same, and therefore, there is a possibility that an overcurrent flows through the switching element serving as the energization path. In particular, since a return current also flows in the high-potential side switching element (in the example of fig. 6, the W-phase switching element 413), the return current is particularly likely to be an overcurrent. Therefore, if the duty ratio at the time of starting the deceleration control is set to-100 [% ] at time x51 as in the reference example shown in fig. 16, there is a possibility that an overcurrent exceeding the allowable current range flows through the drive circuit 41.

Fig. 7 shows a relationship among the motor rotational speed SP, the coil current, and the duty ratio during deceleration control. In fig. 7, the upper stage shows the coil current Ic for the motor rotational speed SP at each duty ratio, and the lower stage shows the duty ratio to be the limit current Ilim. The limit current Ilim, which is the upper limit of the allowable current of the drive circuit 41, is indicated by a one-dot chain line.

In the upper stage of fig. 7, (a) represents that the duty ratio is 0 [% ], (b) represents that the duty ratio is-50 [% ]andthe battery voltage is 12[ V ], (c) represents that the duty ratio is-100 [% ] and the battery voltage is 10[ V ], and (d) represents that the duty ratio is-100 [% ] and the battery voltage is 12[ V ]. As shown in (a), since no induced electromotive force is generated when the motor rotation speed SP is 0, the coil current Ic flowing through the coil 11 becomes a current based on the power from the battery. Further, if the duty ratio is the same, the coil current Ic is proportional to the battery voltage, and if the battery voltage VB is the same, the coil current Ic is proportional to the duty ratio.

When the motor 10 is rotating (that is, when SP > 0), if the duty ratio is 0 [% ], no power is supplied from the battery, and therefore the current flowing through the coil 11 becomes a current based on the induced electromotive force. At this time, the coil current Ic is proportional to the motor rotation speed SP without depending on the battery voltage, and the absolute value becomes larger on the negative side as the motor rotation speed SP becomes larger. When the duty ratio is other than 0 [% ] and power is supplied from the battery, the coil current Ic is the sum of the current based on the induced electromotive force and the current based on the battery voltage VB.

The lower stage shows a lower duty limit value Dlim _ l derived from the relationship between the above (a) to (d) and the limit current Ilim. As shown in (a) to (d) above, when the motor rotation speed SP becomes high, the negative current due to the induced electromotive force becomes high, and therefore, when the negative power supply from the battery becomes high, the allowable current is exceeded. Therefore, in the present embodiment, in order to prevent an overcurrent during deceleration control, the power supply from the battery is limited by limiting the duty ratio in accordance with the motor rotation speed SP.

For example, when the motor rotation speed SP is a value Na [ rpm ] and the battery voltage VB is 12[ V ], the duty ratio needs to be controlled to-50 [% ] or more. In the present embodiment, when the battery voltage VB is 12[ V ], the control is performed with the lower duty limit value Dlim _ l shown by the solid line or the duty ratio on the upper side thereof in accordance with the motor rotation speed SP. When battery voltage VB is 10V, control is performed with lower duty limit value Dlim _ l shown by a broken line or with a duty on the upper side thereof in accordance with motor rotation speed SP. The absolute value of the lower duty limit value Dlim _ l is proportional to (1/VB).

Here, the motor rotational speed SP when the duty ratio is 0 [% ] and the coil current Ic becomes the limit current Ilim is set as the boundary speed Nb. When the motor rotational speed SP is the boundary speed Nb, the coil current Ic is brought to the limit current Ilim by the induced electromotive force with the duty ratio of 0 [% ], that is, in a state where no negative power is supplied from the battery. Therefore, in a region where the motor rotational speed SP is greater than the boundary speed Nb, the lower duty limit value Dlim _ l becomes a positive value. In other words, in the region where the motor rotational speed SP is greater than the boundary speed Nb, the duty ratio cannot be made negative.

In the present embodiment, during deceleration control, the lower duty limit value Dlim _ l is set to be more positive as the motor rotation speed SP increases, and is corrected based on the battery voltage VB. Here, "the motor rotation speed SP becomes more positive as it is larger" means that the control is performed on the upper side than the lower duty limit value Dlim _ l shown in the lower stage of fig. 7, and the absolute value of the duty is smaller than the absolute value of the lower duty limit value Dlim _ l in a region where the motor rotation speed SP is equal to or less than the boundary speed Nb, and the absolute value of the duty is larger than the absolute value of the lower duty limit value in a region where the motor rotation speed SP is larger than the boundary speed Nb.

Fig. 8 is a reference map for reference voltage VB _ r of lower duty limit value Dlim _ l and upper duty limit value Dlim _ h. In the present embodiment, the reference voltage VB _ r is set to 12[ V ]. In the example of fig. 8, when the boundary speed Nb is 3000[ rpm ] and the motor rotation speed SP is less than 3000[ rpm ], the reference lower duty limit value Dlim _ lr is a negative value and is set to be smaller as the motor rotation speed SP is larger, and when the motor rotation speed SP is greater than 3000[ rpm ], the reference lower duty limit value Dlim _ lr is a positive value and is set to be larger as the motor rotation speed SP is larger.

The reference upper duty limit value Dlim _ hr is a positive value, and is set to 100 [% ] when the motor speed SP is 2000 rpm or more, and the reference upper duty limit value Dlim _ hr is larger as the motor speed SP is larger until the motor speed SP reaches 2000 rpm.

Since the absolute value of the duty ratio corresponds to the ratio of the on time, and the current based on the induced electromotive force is considered in the present embodiment, the upper duty limit value Dlim _ h and the lower duty limit value Dlim _ l are set to have different absolute values at the same motor rotation speed SP. The absolute value of lower duty limit value Dlim _ l is smaller than the absolute value of upper duty limit value Dlim _ h.

Fig. 9 is a correction map relating to correction coefficient K1, and correction coefficient K1 is read from battery voltage VB and calculated for lower duty limit value Dlim _ l and upper duty limit value Dlim _ h (see equations (1) and (2)). In the present embodiment, correction coefficient K1 is set such that the absolute values of duty limit values Dlim _ l and Dlim _ h become smaller when battery voltage VB is relatively large, as compared to when battery voltage VB is relatively small. The maps shown in fig. 8 and 9 are examples, and the numerical values may be different. The intermediate value is used by appropriate interpolation such as linear interpolation. The same applies to fig. 14.

Dlim_l＝Dlim_lr×K1……(1)

Dlim_h＝Dlim_hr×K1……(2)

The motor drive control of the present embodiment will be described based on the timing chart of fig. 10. In fig. 10, the common time axis is represented on the horizontal axis, and the motor rotation speed SP, the duty ratio, the correction coefficient K1, the induced electromotive force, and the coil current Ic are represented from above. The coil current Ic is substantially equal to the current flowing in the drive circuit 41. Fig. 12 and 14 are also the same.

At time x11, when there is a range switching request, lower duty limit value Dlim _ l and upper duty limit value Dlim _ h are calculated using correction coefficient K1 corresponding to battery voltage VB, and driving of motor 10 is controlled so that the duty ratio is between lower duty limit value Dlim _ l and upper duty limit value Dlim _ h. From time x11 to time x12, the duty ratio is set to the upper duty limit value Dlim _ h, and the motor 10 is driven by acceleration control. The upper duty limit value Dlim _ h becomes larger as the motor rotation speed SP becomes larger.

At time x12, when the motor rotation speed SP reaches the target motor rotation speed SP, the acceleration control is switched to the steady control. At time x13, when the remaining count to the target count value Cen becomes the stop control start count, the control is switched from the steady control to the deceleration control. At time x13, the drive of the motor 10 is controlled by the lower duty limit value Dlim _ l set in accordance with the motor rotation speed SP and the correction coefficient K1. In the deceleration control, when the motor rotation speed SP decreases, the induced electromotive force decreases, and the absolute value of the lower duty limit value Dlim _ l can be increased, so that the brake torque can be increased more than the deceleration control start time.

At time x14, when the encoder count value Cen falls within a predetermined range (for example, ± 2 counts) including the target count value Cen, the deceleration control is ended, and the motor 10 is stopped by, for example, stationary phase energization. In the present embodiment, control is performed so as not to exceed the upper duty limit value Dlim _ h during acceleration control and so as not to fall below the lower duty limit value Dlim _ l during deceleration control, thereby enabling control to be performed within the allowable current range of the drive circuit 41 over the range switching period.

As described above, the shift range control device 40 controls driving of the motor 10 having the coil 11, and includes the drive circuit 41 and the ECU 50. The drive circuit 41 has a plurality of switching elements 411 to 416, and switches the energization of the opposed coil 11. ECU50 has energization control unit 65 and duty limit value calculation unit 62. The energization control unit 65 controls energization of the coil 11 so that the motor 10 is accelerated and then decelerated to stop the rotational position of the motor at the target rotational position. The duty limit value calculation unit 62 limits the current during deceleration control. This can suppress an overcurrent during deceleration control.

In the present embodiment, the current is limited by limiting the duty ratio in the PWM control, and the duty limit value calculation unit 62 calculates the duty limit value Dlim _ l. The absolute value of the duty ratio is a ratio of the on time, the duty ratio when torque is generated in the same direction as before the start of deceleration control is defined as positive, and the duty ratio when torque is generated in the opposite direction is defined as negative. The duty limit value Dlim _ l is calculated to be negative in the low speed rotation region and positive in the high speed rotation region, and the value increases as the rotation speed SP of the motor 10 increases. The duty limit value is corrected based on the battery voltage VB that is an input voltage to the drive circuit 41. Thus, the energization can be appropriately controlled so that the coil current Ic falls within the allowable range in consideration of the current based on the induced electromotive force.

(embodiment 2)

Fig. 11 and 12 show embodiment 2. In the present embodiment, the correction coefficient K2 used for correcting the duty limit values Dlim _ l and Dlim _ h is calculated based on the current when stationary phase energization is performed at a predetermined duty ratio.

The duty limit calculation process according to the present embodiment will be described based on the flowchart of fig. 11. When a start switch such as an ignition switch of the vehicle is turned on, the ECU50 executes the processing at predetermined cycles. Hereinafter, the "step" in step S101 is omitted, and only symbol "S" is described. The other steps are also the same.

In S101, the ECU50 determines whether or not shift range switching is in progress. In the present embodiment, the shift range switching is performed during a period from when the switching request is input to when the shift range switching is completed. If it is determined that the shift range is not being switched (S101: no), the process proceeds to S102, where the limit correction coefficient calculation completion flag Ffin is invalidated. If it is determined that the shift range is being switched (S101: YES), the process proceeds to S103.

In S103, the ECU50 determines whether the limit correction coefficient calculation completion flag Ffin is set. If it is determined that the limit correction coefficient calculation completion flag Ffin is set (S103: yes), the process proceeds to S109. If it is determined that the limit correction coefficient calculation completion flag Ffin is not set (S103: no), the process proceeds to S104.

In S104, the ECU50 performs stationary phase energization at a prescribed duty ratio (e.g., 40 [% ]). For example, if the UV phase is energized, the switching

elements

411 and 415 are turned on and off at a fixed duty ratio.

In S105, ECU50 determines whether or not a predetermined time X1 (e.g., 20[ ms ]) has elapsed since the stationary phase energization was started. The predetermined time X1 is set based on the time required for the coil current Ic to stabilize. If it is determined that the predetermined time X1 has not elapsed since the stationary phase energization was started (no in S105), the process from S106 onward is not performed. When it is determined that the predetermined time X1 has elapsed since the stationary phase energization was started (yes in S105), the process proceeds to S106, and the coil current Ic is detected.

In S107, the ECU50 calculates the correction coefficient K2 based on the coil current Ic detected in S106. The correction coefficient K2 is calculated by equation (3). Ib in the formula is a reference current when stationary phase energization is performed at a predetermined duty ratio (for example, 50 [% ]) in a reference state. The duty ratio in the reference current detection and the duty ratio in S104 may be equal or different. Further, if correction coefficient K1 in expressions (1) and (2) is replaced with correction coefficient K2, duty limit values Dlim _ l and Dlim _ h can be calculated.

K2＝Ib/Ic……(3)

In S108, the ECU50 sets a limit correction coefficient calculation completion flag Ffin. In S109, ECU50 drives motor 10 by normal energization control so that encoder count value Cen becomes target count value Cen.

The motor drive control processing of the present embodiment will be described based on the timing chart of fig. 12. When there is a range switch request at time x21, stationary phase energization is performed at a prescribed duty cycle. At this time, the motor 10 does not rotate because the energization phase is not switched although the coil 11 is energized. At a time X22 when a predetermined time X1 has elapsed from the time X21, the correction coefficient K2 is calculated using the coil current Ic. The processing from time x22 to time x25 is the same as the processing from time x11 to time x14 in fig. 10.

In the present embodiment, before the start of driving of the motor 10, stationary phase energization is performed at a predetermined duty ratio, and the correction coefficient K2 is calculated based on the coil current Ic at that time. This enables correction in consideration of manufacturing variations, temperature characteristics, and the like, and thus enables more appropriate calculation of duty limit values Dlim _ l and Dlim _ h.

In the present embodiment, the duty limit value Dlim _ l is corrected in accordance with the current when stationary phase energization is performed at a constant duty ratio before the start of driving of the motor 10. This enables duty limit value Dlim _ l to be calculated more appropriately. Further, the same effects as those of the above embodiment are exhibited.

(embodiment 3)

Fig. 13 to 15 show embodiment 3. In the present embodiment, the correction coefficient K3 used for correcting the duty limit values Dlim _ l and Dlim _ h is calculated based on the current when the motor 10 is rotated at a predetermined duty.

The duty limit calculation process according to the present embodiment will be described based on the flowchart of fig. 13. The processing of S201 to S203 is the same as the processing of S101 to S103 in fig. 11. In S204, ECU50 energizes coil 11 at a predetermined duty ratio (e.g., 40 [% ]). Here, since the energization phase is switched according to the encoder count value Cen, the motor 10 rotates.

In S205, it is determined whether or not the rotation of the motor 10 is in a steady state. For example, when the increase in the motor rotation speed in the steady determination time (for example, 20[ ms ]) is equal to or less than the determination threshold (for example, 5[ rpm ]), it is regarded as a rotation steady state. In addition, when the fluctuation range of the coil current Ic is within a predetermined range, the rotation stable state may be considered. If it is determined that the rotation of the motor 10 is not in the steady state (no in S205), the process from S206 onward is not performed. If it is determined that the rotation of the motor 10 is in the steady state (yes in S205), the process proceeds to S206, and the coil current Ic is detected.

In S206, the ECU50 calculates the correction coefficient K3 based on the coil current Ic detected in S206. The correction coefficient K3 was calculated by replacing K2 of equation (3) with K3. The reference current Ib used for calculating the correction coefficient K3 is mapped according to the motor rotation speed SP (see fig. 14), and is set by map calculation according to the current motor rotation speed SP. The mapping operation is not limited to the mapping operation, and the operation may be performed by using a numerical expression or the like. Further, if correction coefficient K1 in expressions (1) and (2) is replaced with correction coefficient K3, duty limit values Dlim _ l and Dlim _ h can be calculated. The processing of S208 and S209 is the same as the processing of S108 and S109.

The motor drive control processing of the present embodiment will be described based on the timing chart of fig. 15. When there is a range switching request at time x31, the motor 10 is rotated at a predetermined duty ratio. When it is determined that the motor rotational speed SP is substantially stable at the time x32 and the motor rotational speed SP is stable at the time x33, the correction coefficient K3 is calculated based on the coil current Ic at that time. Then, when the duty limit values Dlim _ l, Dlim _ h are set using the correction coefficient K3, the control is switched from the control of the fixed duty to the normal control. The processing from time x34 to time x36 is the same as the processing from time x12 to time x14 in fig. 10.

In the present embodiment, the motor 10 is driven at a predetermined duty ratio at a timing before the start of the deceleration control, and the correction coefficient K3 is calculated based on the coil current Ic at a timing at which the motor rotation speed SP is stable. This allows the correction coefficient K3 to be calculated appropriately without delaying the start of driving the motor 10.

In the present embodiment, duty limit value Dlim _ l is corrected based on the current when current is supplied at a constant duty ratio during driving of motor 10 and before the start of deceleration control. This can appropriately calculate duty limit value Dlim _ l while suppressing a decrease in responsiveness.

In the present embodiment, the energization control unit 65 controls energization of the coil 11 by changing the duty ratio so as to accelerate and then decelerate the motor 10 to stop the rotational position of the motor 10 at the target rotational position. Duty limit values Dlim _ l and Dlim _ h are corrected based on the current when current is supplied at a constant duty ratio before the deceleration control is started. Here, the energization at a constant duty ratio may be performed by stationary phase energization in a state where the motor 10 is stopped as in embodiment 2, or may be performed at a constant duty ratio while switching the energization phase in a state where the motor 10 is driven as in the present embodiment. In particular, when the current during motor driving is used for correction, the timing of control at a constant duty ratio is not limited to the start of driving of the motor 10, and may be any timing before the start of deceleration control. Thus, it is possible to appropriately set the lower duty limit value Dlim _ l for limiting the duty ratio on the deceleration side and the upper duty limit value Dlim _ h for limiting the duty ratio on the acceleration side.

In the above embodiment, shift range control device 40 corresponds to a "motor control device", ECU50 corresponds to a "control unit", and duty limit value calculation unit 62 corresponds to a "current limiting unit". Further, the encoder count value Cen corresponds to "a rotational position of the motor", the target count value Cen corresponds to "a target rotational position", and the battery voltage VB corresponds to "an input voltage". The input voltage is not limited to the battery voltage VB, and for example, when a converter or the like is provided between the battery and the drive circuit, the converted voltage may be regarded as the input voltage.

(other embodiments)

In the above embodiment, the motor is a permanent magnet type three-phase brushless motor. In other embodiments, the motor is not limited to a three-phase brushless motor, and an SR motor or the like may be used. In the above embodiment, the coils and the drive circuit are 1 set. In another embodiment, the number of coils and drive circuits may be 2 or more.

In the above embodiment, the motor rotation angle sensor is an encoder. In another embodiment, the motor rotation angle sensor is not limited to the encoder, and a resolver or the like may be used, for example. In the above embodiment, a potentiometer is exemplified as the output shaft sensor. In other embodiments, a sensor other than the potentiometer may be used as the output shaft sensor, or the output shaft sensor may be omitted.

In the above embodiment, 4 recesses are provided in the stopper plate. In other embodiments, the number of the recesses is not limited to 4, and may be any number. For example, the number of the concave portions of the stopper plate may be two, and the P range and the NotP range may be switched. Further, the shift range switching mechanism, the parking lock mechanism, and the like may be different from the above-described embodiment.

In the above embodiment, a speed reducer is provided between the motor shaft and the output shaft. The details of the speed reducer are not described in the above embodiments, but any configuration may be adopted such as a speed reducer using a cycloid gear, a planetary gear, a spur gear for transmitting torque from a speed reduction mechanism substantially coaxial with the motor shaft to the drive shaft, or a speed reducer using a combination of these. In other embodiments, the speed reducer between the motor shaft and the output shaft may be omitted, or a mechanism other than the speed reducer may be provided.

The control unit and the method thereof described in the present invention can be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and the method thereof according to the present invention may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method thereof according to the present invention may be implemented by one or more special purpose computers including a combination of a processor programmed to execute one or more functions, a memory, and a processor including one or more hardware logic circuits. Further, the computer program may be stored as instructions executed by a computer on a non-transitory tangible storage medium readable by the computer. As described above, the present invention is not limited to the above embodiments at all, and can be implemented in various forms without departing from the scope of the invention.

The present invention has been described based on embodiments. However, the present invention is not limited to the embodiment and the structure. The present invention also includes various modifications and modifications within an equivalent range. In addition, various combinations and modes, even including only one of the elements, other combinations and modes above or below the same, are also within the scope and spirit of the invention.

Claims

1. A motor control device that controls driving of a motor (10) having a coil (11), comprising:

a drive circuit (41) having a plurality of switching elements (411-416) for switching the energization to the coil; and

a control unit (50) having: an energization control unit (65) that controls energization of the coil so that the motor is accelerated and then decelerated to stop the rotational position of the motor at a target rotational position; and a current limiting unit (62) that limits the current during deceleration control.

2. The motor control apparatus according to claim 1,

the current limiting unit calculates a duty limit value that limits a duty in the PWM control,

regarding the duty ratio in the PWM control, when the ratio of the on time of the switching element is set to an absolute value, the duty ratio when torque is generated in the same direction as before the start of deceleration control is defined as positive, the duty ratio when torque is generated in the opposite direction to the direction before the start of deceleration control is defined as negative,

the duty limit value is calculated to be negative in a low-speed rotation region, and the duty limit value is increased as the rotation speed of the motor is increased.

3. The motor control apparatus according to claim 2,

the duty limit value is corrected according to an input voltage input to the drive circuit.

4. The motor control apparatus according to claim 2,

the duty limit value is corrected based on a current when stationary phase energization is performed at a constant duty ratio before the motor is started to be driven.

5. The motor control apparatus according to claim 2,

the duty limit value is corrected based on a current when the motor is driven and the motor is energized at a constant duty before the deceleration control is started.

6. A motor control device that controls driving of a motor (10) having a coil (11), comprising:

a drive circuit (41) having a plurality of switching elements and switching energization to the coil; and

a control unit (50) having: an energization control unit (65) that controls energization to the coil by changing a duty ratio so that the motor is accelerated and then decelerated to stop the rotational position of the motor at a target rotational position; and a current limiting unit (62) for calculating a duty limit value for limiting the duty,

the duty limit value is corrected based on the current when the current is supplied at a constant duty before the deceleration control is started.